An ink-jet apparatus in which an ink that can be cured by an active energy ray such as a UV ray (ultraviolet ray) or an electron beam is ejected onto a recording medium with using an ink-jet head, and the ink is cured by active-ray irradiation to form an image has features such as that it is environmentally friendly, and that it can obtain a high-resolution image which can be recorded at a high speed on various recording media, and which hardly bleeds. Particularly, development of an apparatus which uses a UV curable ink is advancing from the viewpoints of easy handling of a light source, compactness, and the like. By taking the advantage of the high-speed fixing property, a so-called single-pass ink-jet apparatus has been proposed in which a web-like recording medium that can be transported at a high speed is used, a head having a width that allows recording to be performed over the whole width of the recording medium is placed so as to be opposed to the recording medium in a state where the head is fixed, and recording is completed simply by causing the recording medium to pass under the head one time. In the case where color printing is performed by using such a single-pass ink-jet apparatus, stationary heads the number of which is equal to that of colors are arranged in the direction of transporting the recording medium. In order to prevent different colors from being mixed with each other in this case, an apparatus in which light irradiating means is placed downstream of each of the heads of the respective colors is disclosed (see JP-A-2004-314586).
On the other hand, in an apparatus having a high productivity, when a web-like recording medium is transported at a high speed, transport wobbling of a base member occurs, and the image quality is reduced. Therefore, an image forming portion must be shortened, and the ink-jet head and the UV irradiating unit are placed in proximity to each other. In this case, there is a possibility that a UV ray which is emitted from the light source, or that which is emitted from the light source and reflected from the surface of the recording medium enters a nozzle face, and inks on the nozzle face and in the vicinities of ejection ports react with UV light to be thickened or cured, thereby causing nozzle clogging or an ejection failure. In order to reduce the quantity of a UV ray entering a nozzle face, an apparatus in which a light trap for capturing a UV ray is disposed between a recording head and a UV irradiating unit is disclosed (see JP-A-2004-167717).
The light trap disclosed in JP-A-2004-167917 is employed in an apparatus of the carriage type. FIG. 5 shows an ink-jet apparatus in which this concept is applied to the single-pass ink-jet system, and which is a premise of the invention. Although the invention will be described with respect to an example of a single-pass ink-jet apparatus, the invention is not restricted to this.
In FIG. 5, 40 denotes the single-pass ink-jet apparatus. In the single-pass ink-jet apparatus 40, the recording medium S is taken out from a recording medium roll 41 which is wound in a roll. First, during when the recording medium S is transported under a full-line ink-jet head 43Y for Y (yellow) color in which many ink-jet nozzles are arranged in the width direction of the recording medium S, a Y-color ink is ejected onto the recording medium S no as to form a desired image. Immediately after the ejection, the recording medium S is passed under a UV irradiation lamp 44. During the passage, the Y-color ink which is a UV curable ink, and which is ejected onto the recording medium S is exposed to UV light to be subjected to semi-curing.
Next, during when the recording medium S is transported under a full-line ink-jet head 43M for M (magenta) color in which many ink-jet nozzles are arranged in the width direction of the recording medium S, an M-color UV curable ink is ejected onto the recording medium S so as to form a desired image. Immediately after the ejection, the recording medium S is passed under a similar UV irradiation lamp 44. During the passage, the M-color ink which is ejected onto the recording medium S is exposed to UV light to be subjected to semi-curing.
Then, during when the recording medium S is transported under a full-line ink-jet head 43C for C (cyan) color in which many ink-jet nozzles are arranged in the width direction of the recording medium S, a C-color UV curable ink is ejected onto the recording medium S so as to form a desired image. Immediately after the ejection, the recording medium S is passed under a similar UV irradiation lamp 44. During the passage, the C-color ink which is ejected onto the recording medium S is exposed to UV light to be subjected to semi-curing.
Finally, during when the recording medium S is transported under a full-line ink-jet head 43B for B (black) color in which many ink-jet nozzles are arranged in the width direction (the direction perpendicular to the plane of the figure) of the recording medium S, a B-color UV curable ink is ejected onto the recording medium S so as to form a desired image. Immediately after the ejection, the recording medium S is passed under a metal halide lamp 45 which is higher in light intensity than the above UV irradiation lamps 44. During the passage, the four-color inks are exposed to UV light to be fixed, thereby completing recording using the four-color inks.
For the purpose of improving the productivity, enhancements of the sensitivity of an ink and the energy or a UV irradiation tamp are attempted.
On the other hand, on the lower face of each of the ink-jet heads 43, the ink is easily cured by leakage light from the UV irradiation lamps 44. In order to allow the ink-jet head 43 to stably perform the ink jet ejection for a long term, in the apparatus of FIG. 5, a light capturing portion 47 is interposed between the ink-jet head 43 and the UV irradiation lamp 44, so that leakage light from the UV irradiation lamp 44 does not reach the ink-jet head 43.